Reddit is removing the Direct Message feature, and all active conversations will be archived so you won’t be able to continue ongoing conversations. Reddit also deleted all bad reviews for their app awhile ago. Its rating went from 3.4 to 4.5 stars overnight.
It was useful for asking questions that neither you nor the other person would want to put in a public post. For example, someone posted a picture in the bad real estate sub that looked very familiar, and I sent a DM asking “is this X location?”. I might not want people to know I’m familiar with X location, they might not want people to know they’re familiar with X location, but maybe we’re both ok with each other knowing.
But I’m pretty sure its main use was sending hate to people without getting banned.